Our narrator is absolutely all-knowing in the truest sense of the word. He sees and hears just about everything, and instead of narrating events from the point of view of just one two people, he opts to follow almost one hundred different characters on their adventures throughout the course of the story.
That's a lot of action to keep track of, but there's a perfectly good reason for taking on such a daunting task. This strategy allows him to give a comprehensive tale of not just Arthur or those close to him, but of the whole Round Table. For example, when he narrates the Grail Quest, he does so in episodes, following Galahad for a while, then Gawain, then Launcelot, then returning to Galahad, etc. He can interweave the characters' stories, as when Percyvale, Bors, and Galahad emerge from their separate adventures during the Grail Quest to set sail on a mysterious ship together and achieve the quest.
And while we may takes sides in various feuds, rooting for Launcelot, Trystram, or even Gawain, the narrator of Le Morte D'Arthur remains pretty objective. He rarely gives his opinions on the goings on in Camelot. Because they're so rare, the few moments when he does, however, tell us a lot about what interests him most about his story.
For example, when the people of England defect from Arthur in favor of Mordred, the narrator launches into a long diatribe about the lack of loyalty of the English people, which he compares to the "new fangill"-ness of the modern English people (680.25&ff). Likewise, the narrator puts the devoted love between Launcelot and Gwenyvere on a pedestal in comparison to that of lovers "nowadayes" who lack "stabilyté," or faithfulness (625.3&ff).
Not only do these examples tell us that the narrator really values loyalty, but they also tell us that he sees Arthur's story as having important parallels to his own time, maybe even teaching some important lessons. So while he may be mostly objective about Camelot drama itself, he's got a whole slew of opinions about what that drama can shed light on in his England.